This invention relates generally to the field of vapor compression air conditioning and refrigeration systems. More specifically, the invention relates to a method, as well as an apparatus for practicing the method, for detecting the presence, as a contaminant, of one type of refrigerant in a system that uses another type of refrigerant.
A large proportion of the air conditioning systems in use today use chlorofluorocarbon (CFC) based refrigerants. There is, however, wide acceptance of the proposition that chlorine contributes to the destruction of the earth's ozone layer and that use of CFC-based refrigerants leads to the introduction of chlorine into the atmosphere. In an effort to slow or halt the rate of ozone depletion and in response to governmental mandates, manufacturers are using alternative refrigerants, containing less or no chlorine, in newer air conditioning systems. As a result, maintenance personnel are more and more likely to encounter air conditioning systems using non-CFC based refrigerants.
In general, one should not mix CFC and non-CFC based refrigerants in the charge of a single system. System materials compatible with one refrigerant type are frequently not compatible with another refrigerant type. For example, lubricating oils are commonly added to the refrigerant charge in a system to provide lubrication to system components such as the compressor. Lubricating oils suitable for use with CFC based refrigerants are not compatible with non-CFC based refrigerants. Use of the improper lubricating oil or charging a system with the incorrect refrigerant can lead to significant, even catastrophic, damage to the system.
The application with perhaps the highest potential for system damage due to charging with an improper refrigerant is in automotive air conditioning. The automotive industry is phasing out systems using CFC refrigerant R-12 in favor of systems using non-CFC refrigerant R-134a, both in newly manufactured systems and by conversion of existing systems. Newly manufactured automotive air conditioning systems bear prominent markings identifying the type of refrigerant used by the system but older systems do not. There is a greater likelihood that untrained and unqualified persons will attempt to service automotive air conditioning systems than other systems used in other applications. Charging R-12 into a system using R-134a can lead to component failures of such magnitude that repair may require replacement of the entire system. Charging R-134a into a system using R-12 can produce the same result.
Because of the increased possibility of system contamination by charging an improper refrigerant, there is a need for a way for maintenance personnel to detect such contamination as an aid in troubleshooting as well as to evaluate warranty claims. There is a concomitant need for an apparatus to practice the method. Such a refrigerant testing apparatus should be relatively inexpensive, simple to use and produce accurate results.
Although R-12 and R-134a differ in chemical composition, they are both colorless and their saturation temperatures and pressure characteristics are so similar that it is impossible, in a workshop environment, to distinguish between the two using such means as sight or pressure and temperature measurements. Some other method of distinguishing between the two is required.